1. There Was No "United States" in the Declaration of Independence.
When the Founding Fathers adopted "The unanimous Declaration of the thirteen united States of America" [wiki] on July 4, 1776, they didn't form the nation called The United States of America.
Indeed, the United States of America actually came into being on March 1, 1781 when the Second Continental Congress ratified the Articles of Confederation and Perpetual Union (or more commonly known as the Article of Confederation [wiki]).
2. Jefferson Was Upset that Slavery was Edited out.
In his first draft of the Declaration of Independence, Jefferson [wiki] listed the British crown's support and importation of slavery to the colonies as one of the grievances:
"He has waged cruel war against human nature itself, violating its most sacred rights of life & liberty in the persons of a distant people who never offended him, captivating & carrying them into slavery in another hemisphere, or to incur miserable death in their transportation thither."
The passage, however, was edited out by request of the delegates from South Carolina and Georgia. Jefferson (himself a slave owner!) remained upset about this removal of the condemnation of slavery until his death.
3. The Youngest and Oldest Signers
The youngest signer of the Declaration of Independence was Edward Rutledge [wiki] of Southern Carolina. He was 26. Actually that wasn't the only interesting thing: Rutledge argued for the deletion of Jefferson's condemnation of slavery (see above). He was also initially opposed to independence, but signed the Declaration for the sake of unanimity.
The oldest signer was Benjamin Franklin [wiki], who was 70 at the time. At the signing, Franklin famously said "We must all hang together, or, most assuredly, we shall all hang separately."
4. The Sole Recanter: Richard Stockton
During the course of the Revolutionary War, four signers were captured by the British (George Walton, Thomas Heyward, Jr., Arthur Middleton, and Edward Rutledge) while fighting. Although they were treated harshly, all four were eventually released.
Only one guy, Richard Stockton [wiki] of New Jersey, was captured in the middle of the night and taken prisoner specifically because he was a signer of the Declaration. Stockton also had the singular misfortune of being the only recanter of the oath to support the Declaration of Independence with "our Lives, our Fortunes, and our sacred Honor." Under duress of harsh British confinement, Stockton recanted his signature on the Declaration and declared his allegiance to the King George III before he was released. (Source: American Heritage).
Stockton's ordeal didn't end there: his estate was taken by the British army during his absence, and all of his household belongings were taken or destroyed. The imprisonment not only broke Stockton's mind and spirit, but also ruined his health - it took him years to fully recuperate. Before he died, Stockton re-affirmed his oath of allegiance to the United States.
5. Bargain Hunter Bought an Old Copy of the Declaration of Independence for $4, Sold It For Millions!
In 1989, a bargain hunter who bought an old and torn painting for $4 at a flea market found an old copy of the Declaration of Independence tucked away between the canvas and the frame!
A copy of the Dunlap Broadside, now at Yale University.
It turned out to be one of the 200 official copies from the first printing of the Declaration of Independence, called the Dunlap Broadsides [wiki]. Before this discovery, only 24 copies were known to exist.
The lucky bargain hunter sold his copy of the Declaration at an auction for $8.14 million!